Terephthalic acid di-esters, such as Di-n-butyl terephthalate, also known as DBT, can be used as plasticizers in a variety of polymeric materials such as polyvinyl chloride. Eastman Chemical Company produces di(2-ethylhexyl) terephthalate, also known as DOTP or 168 Plasticizer, by the titanate-catalyzed transesterification of dimethyl terephthalate (DMT) with 2-ethylhexanol. A more direct route to this product has been described in parent U.S. patent application Ser. No. 11/699,652 wherein terephthalic acid (TPA) is reacted with 2-ethylhexanol using a titanate catalyst, with reaction condition involving either pressure or ambient pressure through use of a fractionating column. However, titanate catalyst cannot be used directly to produce di-n-butyl terephthalate (DBT). The present inventors have discovered that excess strong acids, such as methane sulfonic acid and sulfuric acid, in combination with a fractionating column overcome this problem.